The final air-dried product is pure except for its moisture content, as is shown by the fact that on drying in vacuo it has a very good melting point. A sample of Kahlbaum's nitroso-b-naphthol melted at 101—105.
3. Other Methods of Preparation
Nitroso-b-naphthol has been made by the action of hydroxylamine hydrochloride on b-naphtho-quinone-chlorimide;[1] by the action of sulfuric acid upon a solution of potassium or sodium nitrite and the sodium salt of b-naphthol;[2] by the action of sodium nitrite upon an alcoholic solution of zinc chloride and b-naphthol;[3] by the action of sodium nitrite upon b-naphthol suspended in zinc sulfate solution;[4] by the action of nitrous acid on b-dinaphthol methane;[5] and by the action of nitrosyl sulfate upon the sodium salt of b-naphthol.[6]
[1] Ber. 27, 241 (1894).
[2] Ber. 8, 1026 (1875); 27, 3076 (1894); J. Chem. Soc. 45, 295 (1884).
[3] Ber. 18, 705 (1885).
[4] D. R. P. 25,469; Frdl. 1, 335 (1883).
[5] Ber. 33, 806 (1900).
[6] J Chem. Soc. 32, 47 (1877); Ann. 189, 146 (1877).